Electrostatic storage devices



Oct. 16, 1956 s. HANSEN ELEcTRosTATIc STORAGE DEVICES 4 Sheets-Sheet 1 Filed Jan. 12, 1952 Oct. 16, 1956 s. HANSEN 2,767,345

' ELEcTRosTATIc sToRAcanEvIcEs Ilflflfvv- |l 4 Oct. 16, 1956 s. HANSEN ELECTROSTATIC STORAGE DEVICES 4 Sheets-Sheet 4 Filed Jan. l2; 1952 mmwx 47m/Min United States Patent aan 2,7 67,3435 ELECTRSTATIC STOliAGE Siegfried Hansen, Los Angeles, Calif., assigner, by mesne assignments, to Hughes AircraftCornpany, a corporation of Delaware Application January 12, 19.52, Serial No. goed@ 24V Claims. (Cl. 315i1 2)' This invention relates to electrostatic storage systems and more particularly to memory tube systems for use in regenerating the charges on a series of spots on the tube or storing a new series of charges on a series of previously charged spots while simultaneously producing an output signal representing the previous charges.

In the digital computer art, memory tubes are ernployed asthe principal components of electrostatic storage devices for storing a series of binary digits in the form o f .a corresponding series of charged spots, respectively, yonthe screen of the tube. Generally, the charge on any spot .may `have one of two values representing the two binary digits, respectively. Owing to the loss .of charge ,with time through electron redistribution, transverse leakage, etc., with the resultant loss of the stored digital information, it is necessary to regenerate the charge on each of the spots at regular intervals in order to retain the stored `information for an indefinite period of time. Furthermore, in digital Vcomputer operations it'is *often required to derive an output signal representing .the stored binary digits without disturbing the charges, or to replace the stored char-ges .with a new series of charges representing a new series ofbinary digits. Y

The ,prior art electrostatic storage Vdevices generally have performed each of the above functionsbyat `least two separate and distinct Vsteps which, therefore, are time consuming and require additional equipment.V -l'ior'ex'arnple,"in performing the regenerating function, prior art devices regenerate the Vspot charges by a .first operation, and produceV an output signal representing the charges b y a second operation. Similarly, the prior artdevices `require at least three distinct `operationsto perform the function of storing a new series of binary digits and producing an output signal representing thepreviously Vstored char-gels'. For example, to perform this latter function, the prior ,art devices sample the charge of eaohspot 4to .produce an output signal representing the charge, erase the spot in another operation, and then store the new binary digit on each erased spot by still another operation.

v'The present invention discloses memory tube electrostatic storage systems which overcome the above and other disadvantages of the prior art devices ,in ,performing eachof the above-noted functions. .In particular, the systems of the present invention automatically and simultaneously produca'upon the Vregeneration ofthe charge ofneach spot, an output signal having a voltage level corresponding to the binary digit represented by the Vstored charge. Furthermore, the system of the present linvention is capable of 'storing a new series of binary digits directlyon a series of previouslycharged spots, `and simultaneously, with the storage of each new digit, producing an output signal representing the charge previously storedon Vthe spot. In this manner, each desired function is performed in a single operation bythe systems of the present invention. i

Two embodiments of the present invention are illustrated, .oneemployinga conventional cathode ray tube as 2,757,345 Patented Get. 16, l

mines the function vwhich the device performs. Thus, if

it is `desired to storeV a new series of digits, the flip-hop vis setto vproduce appropriate output voltage level signals by signals representing the new digits to be stored. Y lf it Ais desired to regenerate previously Vstored charges, the iiip-ilop'is set'by signals derived from the previously stored charges, and thus each spot may berechargedv to its exact initial charge value before leakage, etc., causes a deviation therefrom. During the storage of a new series of binary digits on a series of spo/ts which had Ibeen previously charged to represent a previous series of `ligits, or during the regeneration of a previously stored series of spots, an output signal representing the previous series of digits is produced by a mixing network which `mixes the output signal from the ilipflop and a signal derived from the charging of the spot to its new charge. According to the present invention, there is provided an electrostatic storage device including a memory tube; actuable means ,responsive to applied signals for producing a first output signal to control the storing of'charges within the memory tube; output means for producing'a A'second output signal when the charge being stored on a spot does not correspond to the charge previously stored thereon; i1- st selectivelyoperable means forapplying s aid second output signal to said actuable means to actuate said actuable means to restore a previous charge level on a spot; second selectively operable means 4for `actuating said actuable means to store' a new charge lev'el on aspot; and means for combining Vsaid iirst andsecond output signals to produce a third output signal representing the previous charge on a particular spot.

Therefore, an object -of the present invention is to provide a system for selectively either regenerating the previous charge on a spot on the Vstorage,electrode of a memory tube, or storing anew charge on the spot while, simultaneously therewith, producing an output signal representing the previous charge.

'Another object of the present invention is to provide a system for selectively either regenerating the previous charge on a spot on the Vstorage electrode of a memory tube and producing an output signal representing the previous charge, or storing a new charge on the spot while simultaneously ltherewith producing an output signal representing the previous charge, the previous charge being either a relatively positive Vor a relatively negative charge level and the new charge being either said positive or said negative charge level. l

A further object of the present invention is to provide a system for regenerating the charge on a spot on the storage electrode of a memory tube, said spot yhaving been previously charged to either `a relatively positive or a relatively negative charge level and, simultaneously therewith, producing lan output signal representing the charge level. v A'still further object of the present invention is to provide a system for regeneratingt-he charge on a spot on the phosphorescent layer of a cathode ray tube, said tube having an external conductive coating adjacent .the layer and said spot having been previously charged to either a relatively positive or a relatively negative charge 'level'.

A still further object of the present invention is to provideA a system for regenerating the charge on a ,spot ion the targetelectrode of a storage tube, said spot having been previously charged to either a `relativelypositive or a relatively negative charge level.

Another object of the present invention is to provide a system for simultaneously storing a new charge on a previously charged spot on the storage electrode of a memory tube, and producing an output signal representing the previous charge.

Still another object of the present invention is to provide a system for storing a new charge on a spot on the phosphorescent layer of a cathode ray tube, said spot having been previously charged to either a relatively positive or a relatively negative charge level and the new charge being either of said positive and negative charge levels, said device producing an output signal representing the previous charge simultaneously with the storage of the new charge.

Still another object of the present invention is to provide a system for storing a new charge on a previouslycharged spot on the target electrode of a storage tube and, simultaneously producing an output signal representing the previous charge.

The novel features which are believed to be characteristic of the invention, both as to its organization and method of operation, together with further objects and advantages thereof, will be better understood from the following description considered in connection with the accompanying drawings in which several embodiments of the invention are illustrated by way of examples. It is to be expressly understood, however, that the drawings are for the purpose of illustration and description only, and are not intended as a definition of the limits of the invention.

Fig. 1 is a circuit diagram of one embodiment according to the present invention;

Figs. 2 to 4 are composite diagrams of waveforms of electrical signals appearing at various points in the device according to Fig. l; and

Fig. 5 is a circuit diagram of another embodiment according to the present invention.

Referring now to Fig. l, there is illustrated one embodiment of the present invention including a cathode ray tube 11 having an electron gun 12, horizontal deiiection plates 13, and vertical detiection plates 14, all sealed within a glass envelope 1S. Also included in tube 11 are a collector electrode 15 and a phosphorescent layer 16, both applied as coatings on the inner surface of glass envelope 18. Applied to the outer surface of envelope 18, opposite layer 16, is a coating 2f? of conductive material, such as an Aquadag coating, a colloidal dispersion of finely ground graphite manufactured by the Acheson Colloids Company of Port Huron, Michigan. A source 21 of high voltage and a source of high frequency energy, such as a 30 megacycle oscillator 22, are coupled to electron gun 12, source 21 and oscillator 22 producing through gun 12 a 30 megacycle current-modulated electron beam 19 which strikes phosphorescent layer 16.

A pulse source 24 has its output terminal connected to the input terminal of a first stepped waveform generator 2S, the stepped waveform output signal of which is applied to horizontal deflection plates 13. A second stepped waveform generator 26 has its input terminal connected to the output terminal of generator 25, the stepped waveform output signal of generator 26 being applied to vertical defiection plates 14. The connection between generators 25 and 26 is so arranged that the output signal of generator 25 completes a full cycle of steps during the interval that the output signal of generator 26 completes a single step in cycle. One such arrangement is disclosed in copending United States application for patent, Serial No. 241,997, filed August 15. 1951, for tepped Signal Producing System by Siegfried Hansen, now Patent No. 2,709,770. The application of the respective output signals to the deflection plates of cathode ray tube 11 causes beam 19 to strike iayer 16 1n a series of spots, one spot being produced by each step of the output signal of generator 2S, and one lineof spots being produced by each step of the output signal of generator 26.

A first end of the primary winding of a transformer 28 is coupled to coating 20, while the second end of the primary winding is coupled to ground through a capacitor Z9. The secondary winding of transformer 28 has one end coupled to a tuned amplifier 30, and the other end coupled to ground. The output signal of amplifier 30 and the output signal of oscillator 22 are applied to the two input terminals, respectively, of a phase detector 31. Amplifier 3f) is a conventional tuned amplifier and is tuned to amplify a 30 megacycle signal. Phase detector 31 may be of the type illustrated in Fig. 21S on page 332 of the book Principles of Radio Engineering by R. S. Glasgow, published in 1936 by the McGraw-Hill Book Company, New York and London, in which the output signal of amplifier 3f) is applied at B, the signal from oscillator 22 at A, and the output of the detector taken at D, where A, B and D are points in the circuit diagram found in Fig. 218, of the cited reference.

The output terminal of detector 31 is connected to the input terminal of a first differentiating circuit 34 through a phase inverter 33, and is connected directly to the input terminal of a second differentiating circuit 35. The output terminals of differentiating circuits 34 and 35 are coupled to one input terminal of each of two-terminal and gate circuits 36 and 37, respectively. Each of circuits 36 and 37 has its other input terminal connected to an output conductor 4th of a device 39 for producing an output signal of alternate relatively high and low voltage levels. The output terminals of circuits 36 and 37 are coupled to input conductors 42 and 43, respectively, of a device 41 similar to device 39.

Devices 39 and 41 each may be a conventional flip-flop which produces a first output signal of alternate voltage levels on a first output terminal and a second output signal, of levels complementary to those of the first output signal, on a second output terminal. For example, as shown in Fig. l, device 39 is a flip-flop which produces its first and second output signals on conductor 40 and a conductor 44, respectively. Similarly, device' 41 is a flip-flop which produces its alternate voltage levels` in response to negative input signals being applied alternately to input conductors 42 and 43. Only one input signal of flip-flop 41 is utilized in the circuit of Fig. 1, this output signal appearing on an output conductor 54.

Output conductor 44 of flip-flop 39 is coupled to one input terminal of each of two-terminal and gate circuits 46 and 47, the output terminals of circuits 46 and 47 being coupled to input conductors 42 and 43, respectively, of flip-flop 41. The other input terminal of circuit 46 is coupled through a differentiating circuit 48 to one output conductor 51 of the flip-flop 53, while the other input terminal of circuit 47 is coupled through a differentiating circuit 49 to the other output conductor 52 of ip-tiop 53.

Output conductor 54 of flip-flop 41 is coupled through an attenuation network 5S to the second end of the primary winding of transformer 2S. This second end of the primary winding is also coupled to an output terminal 59 through a mixing resistor S6, the output terminal of phase detector 31 being coupled to output terminal 59 through another mixing resistor 57. A resistive load device 6G is illustrated as connected between output terminal 59 and ground.

A storage device, according to Fig. l, may perform any of the following functions: store a series of binary digits in the form of charges on a series of spots on phosphorescent layer 16 contacted by beam 19; regenerate the charge on each of a series of spots already charged to thereby maintain, indenitely, the storage of a series of binary digits; or store a new charge on each of a series of spots to represent a new series of binary digits while simultaneously producing signals representing the preViOuSly stored binary digits. The levels of the output .signals @fsm-flop e9 @e1-tenerse @nevenfuncties t .be Psrfermed bythe eteragedeviee .Referriristlew tfLFis. ,2, `there is shown@ eelrlposte diagrlarn;of the waveforms ofsi'gnalsoccurring at various Vpoints in the circuitof Fig. l during `the interval in which thestoragerdevice is performingrtlhe v`first-meutioned function, that is, the.storage of a sreriesuofvbinary digits. During this interval, the Signal, generally Adesignated 1.4.4. anpearrinaen Output eeildiletor .44 0f flprep 3 9, his. ata high Avoltage level 41,4a. At the Sametime, the signal, generaux/.designated all', .appearing en `enfant eeadiletori @filip-.liep i39 is at a lowvaltege .level Alta. Level ,4.441 ofsignal 444 is of s uicientamplitude to open gate circuits 46 and 47, 4vvhile level 4tlg .ofisignal 40' is finsulicient to opencircuits `36 and 37.

' 'lrfhebinary digits to be stored are represented bythe highand low voltage levels ofthe signal, generally desatedSgZ'lin Fig. `2, produced on outputconductor 5:2 `if ip-flopfS. The 10W voltage levelimay, by definition, -representthe binary digit 0,while thevhigh voltage level `represents the binary digit l. Ihe signal, `generally tdesignated-24 of Fig. "2, is 4the output -,signal ofpulse source 24, and includes aseries ofnegative pulses occurring `at regular intervals. As `,will be apparent from .the .discussion ofthe operation of pulse source ,2 4, and n /laveforrngenerators 25 and 26 as found inthe before- .mentioned `application for patent Serial No. 241,997, each successive pulse produced by source 2 4 .results .in amdifferent step being ,produced by generator 25 which, in turn, causes electron beam 19 to strike a dilferent spot on layer 156. Thus, since the voltage levels .of signal .52 occur during the successive interpulse `inter-.vals of signal 24', it is apparent that the `charging voltage applied to tube 11 willbeconstant during the interval that '.beam 19 strikes a given spot on layer 16.

The `signal appearing on output conductor l51 of flip- :flop 53 is `designated generally as 51 in Fig. 2, and `includes voltage levels complementary to the levels of signal 52'. Signals 5,1 and `52 are differentiated by `circuits 48 and 49, respectively, to produce signals ,46' and 4'7', respectively. As shown in Fig. 2, signal 46' illcludes a series of alternately negative ,and positive r,polarity pulses, each pulse beingV aligned in time with ,2t-transition point of signal 51' from one level to another. Similarly, signal 47 includes a series of alternately posi- -tive and negative polarity pulses corresponding tothe transition points, respectively, of signal 5.2. The pulses of `signal 46' occur simultaneously with the pulses of signal 47',.but are of opposite polarity. Signals V,46' and 47' are applied to gate circuits 46 andr47, respectively.

Each of gate circuits 46 and 47 may be of the type Villustrated in Fig. `l of copending United States Application for Patent, Serial No. 245,860, tiled September 1Q, 1951, for High Speed Flip-Flop Counters by Eldred C. Nelson, and as such, pass only negative pulses when opened. Thus, negative pulse 46a of signal 46' is passed byrcircuit 46 to input conductor 42. Pulse 46a triggers iiip-flop 4l to produce a high voltage level 54a of the signal 354 on output conductor 54 during the first interpulse interval. Pulse 47a of signal 47', appearing rsimultaneously with pulse 46a, is not passed by gate circuit ,4f/lowing to its positive polarity, and hence, has no effect onthe conduction state of flip-flop 41.

i The second differentiated pulse46b of signal 46 is of .positive polarity and is blocked by circuit 46, but the second pulse 47h, of signal 47', is of negative polarity and Vis thus passed by gate circuit 47 to input conductor 43. Flip- .op 4l is thereby triggered to produce the low voltage level 54h of signal -54 during the second interpulse interval. The remaining Voltage levels of signal 154' are formed by signals 46' and 47 in the manner eX- `plained :for the first two interpulse intervals.

Signal 54' is attenuated by attenuation network 55, andlthe resultant attenuated signal is Vapplied through the `primary winding-of transformer 23 to coating 20. -Before proceeding further with the description of the mari- `nerby which the voltage levels of signal 54 are stored inthe form of charges onlayr '116, it will be helpful to review briefly the "principal operational characteristics vo'fcatholde raytube V-11 when utilizedasfa rnemorytube.

Phosphorescentflayer i6 has secondary emissive prop- ;erties similar to the properties possessed by dielectric materials-found on the target electrodesof conventional storage tubes. Any given spot'on layer l6,`when struck by electron beam `19, will'emit a number of secondary emission electrons greater than the number of primary electrons originally present in the portion of'bearn 419 striking the given spot. These secondaryeniissio'nelectrons have two main paths of traveli 'they may bedrawn to collector electrode 15, maintained at ground potential, or they may return to the `same spot from whichrthey were liberated. The proportion of "the "seconda-ry emissionvelectrpns travellingito electrode l5 to those returning to the lVsame spot Von layer 16 is affuncti'on oflthe voltage applied to`coating 20. Thus, if `coating V20 were held at a 'positive VlO-volt level, for cxampledarnajority of the secondary emission electrons would be attracted, through condenser action between'coating Ztl and layer 16, `back to the Vsame spot from which they .were initially liberated. Therefore, uponrernovjal of the electron beam runder such conditions, the given spot will containmore electrons than it-had before being struckby `the beam, and henceerhibit a relatively negative charge. if, however, coating VZtl were maintained at justnabove Vground potential, for example vl volt positive, aigreateryproportion of the secondary emission electrons wouldv be drawn to collector electrode 15 rather Vthan to the spot 'fro-rn `which they were liberated. Upon removal of the electron beam, the lgiven spot wouldcontain fewer electrons than l it had before being struck b'y'theibeam, andhence eithibit a relatively positive charge. It is assumed 4here lthat the relatively positive charge represents the binary digit VO and the relatively negative Vcharge representstlie binary digit 1. l u i A' leturningnow to the description of the .operation of the circuit'of-'Fig 1r, attenuationnetwork 55 is employed to reduce the high and low voltage levels of 5 4' to approximately l0 and Y1 volts positive, respectively,1 by way of example. The pattern, generally designated 16' of Fig 2V, `illustrates the charge levels placed `onuaseries of spotson layerl by electron beam 19 undenthe control of the Successive voltage `levels -of Signal54' after attenuation by attenuation network 55. 'I-he high voltagelevel 54a of signal 54' produces a relatively negative ,charge level 16a of pattern 16' onithe iirs't spot contaeted while the low voltage level 544i: of signal 54' produces a relatively lpositive charge level 1Gb of pattern 16on the second spot contactedketc. A comparison of signal 52', representing the series of digits to be stored, Aand pattern 16' reveals that the charge on each spot corresponds to the voltage level 'of rsignal 52"during the interval that beam -19 is strilring the spot. Airelatively positive charge'corresponds to a low voltage )level of signal 52', while a relatively negative charge -corresponds to a high voltage level of signal 5`2,Vrepres`entinig, according to the conventionsrpreviously adopted,ibinaryu0 and binary l digits, respectively. i i 4Fllhe second-mentioned function capable `of ybeing performed by the storage device of 1 is `that of 'riegenerating the charges previously stored on a series of spots, and the manner in which this result is`,accomplished is 4illustrated by the signal waveforms shown in Fig. 3. Under ordinary conditions, the spot charges will be dissipated in a reasonably short period of time owing-Ato `the transverse leakage of'phosphorescent layer 16, electron redistribution, etc. V.1"ccordingly, if the binary digits thus stored are to be retained indeinitely, the luchar-ge of each spot rnust be regenerated or brought baciato Vits 4original value at occasional-intervals. i

IFor the purposes of this explanation, assume that the vflip-iiop 39 is triggered so that signal 44 is at a 10W voltage level 44b and signal 40 is at a high voltage level 4Gb, as shown in Fig. 3. Signal 24 is illustrated again in Fig. 3, in order to permit a clearer understanding of this function of the device.

Under the conditions outlined above, gate circuits 36 and 37 are open and gate circuits .46 and 4,7 are closed. Accordingly, the state of Hip-flop 53 is immaterial to the regenerating function of the storage device of Fig. 1, and the state of hip-flop 41 is controlled by the signals appearing at the output terminals of circuits 36 and 37. Since the level of signal 54 at the beginning of the regenerating function, is immaterial, it will be assumed that signal 54 is initially at its low voltage level.

Now, during the rst interpulse interval of signal 24', beam 19 strikes the first spot of layer 16, this spot being charged to negative charge level 16a of pattern 16". Since signal 54', applied through network 55 and the primary winding, is initially at its low voltage level, the spot tends to discharge toward the positive charge level. Owing to the 30 megacycle frequency of beam 19, a low capacity reactance exists between layer 16 and coating 20, and the change of charge on the spot is reflected through condenser action as a 30 megacycle current in the primary winding of coil 28. Capacitor 29 is of such value as to series resonate with the inductance of the primary winding of transformer 28 at the 30 megacycle frequency thereby causing an appreciable voltage drop to appear across transformer 28. This voltage drop is amplified by tuned amplifier 30, and the amplified signal thereof is detected by phase detector 31 to produce a signal corresponding to the envelope thereof. The 30 megacycle current flowing in the primary of transformer 2S when a spot is being charged in a positive direction will differ in phase from the current flowing when a spot is being charged in a negative direction, and, consequently, the output signal of phase detector 31 will be an indication of the change of charge a particular spot is undergoing.

The output signal of detector 31 is inverted by phase inverter 33 and the inverted signal is differentiated by differentiating circuit 34. The differentiated signal, generally designated 34 of Fig. 3, includes first pulse 34a of negative polarity corresponding to the initial change in charge.

The negative polarity of pulse 34a may be established by connecting phase detector 31 so that the output signal from the phase detector is of relatively negative polarity when a spot is being charged in a positive direction, and of relatively positive polarity when a spot is being charged in a negative direction.

Pulse 34a, upon being passed by gate circuit 36, triggers ip-iiop 41 such that high voltage level 54a of signal 54 is produced on conductor 54. This high voltage level 54a, after attenuation by network 55, causes the charge on the iirst spot to return to its original negative charge level 16a of pattern 16".

The second spot scanned by beam 19, during the second interpulse interval, had originally a positive charge level 1Gb. Since signal 54 is at its high voltage level 54a during this interval, a modulated change of charge signal is produced in transformer 23 of opposite phase from that produced when the first spot was contacted. Thus, a positive pulse 34b of signal 34 is produced at the output of differentiating circuit 34. Pulse 3412 will not be passed by gate circuit 36 owing to its positive polarity. However, a corresponding negative pulse 351; appears simultaneously therewith in the complementary signal, generally designated 3S in Fig. 3, produced on the output conductor of differentiating circuit 35. Negative pulse 35b will be passed by gate circuit 37 and will trigger flip-flop 41 into its other conduction state, whereby a low voltage level 54b of signal 54 is produced during the second interpulse interval. This low voltage level corresponds to the original positive charge level 16b of pattern 16 and thereby causes the spot to return to its original charge level.

The next or third spot had originally a positive charge level 16C, the same as level 16h, and the low voltage level 54h of signal 54' is thus retained during the third interpulse interval and thereby causes the spot to return to its initial charge level. The remaining portions of the signals and patterns illustrated in Fig. 3 may be readily understood from the explanation of the operation during the first three interpulse intervals, as set forth above.

When signal 54 is at the voltage level corresponding to the initial charge on a given spot, and the charge on the spot has deviated from its exact initial charge value, the subsequent recharging thereof back to its initial value will produce modulated charging currents in transformer 28 resulting in complementary pulses appearing in signals 34 and 35. However, these pulses are of much smaller magnitude than the pulses produced when the conduction state of iiip-op 41 is initially reversed from that necessary to bring the charge of a given spot back to its original value, as described for the first and second spots of Fig. 3. The smaller recharging pulses will be of insuicient magnitude to trigger iiip-flop 41 thus allowing the desired operation of the circuit as set forth above.

The signal appearing on output terminal 59 is a function of the voltages applied from detector 31 and attenuation network 55 to resistors 57 and 56, respectively, and the relative resistance values of resistors 56 and 57 and load device 60. If the resistances of resistors 56 and 57 are equal in value and each twice the value of the resistance of load device 69, the voltage appearing on terminal 59 is equal to one-fourth of the sum of the voltages of the applied signals. It is thus seen that the signal outputs of attenuation network 55 and detector 31 may be mixed by resistors 56 and 57 so that each contributes the same relative amount to the output signal appearing on terminal 59. In the case where the storage device of Fig. l is utilized to store a series of binary digits on a series of spots which have not been previously charged, or whose charges are no longer of interest, the voltage levels representing the binary digits to be stored may be taken, if needed elsewhere for computation purposes, directly from output conductor 52 of Hip-flop 53.

Where the storage device is used to regenerate the spot charges, the signal appearing on terminal 59 is derived almost solely from the output conductor of attenuation network 55 since the triggering pulses appearing on the output conductor of detector 31 are of inconsequential duration. The voltage levels of the output signal in such a case will be of one-fourth the magnitude of the voltage levels appearing on the output conductor of attenuation network 55 owing to the action of mixing resistors 56 and 57 and the fact that no sustained signal is applied to resistor 57 from phase detector 31, and the signals will thus be seen to represent the previously stored binary digits.

The last-named function of the storage device of Fig. 1 is that of storing a new series of binary digits in the form of charge levels on a series of spots previously charged to represent another series of binary digits, and deriving simultaneously therewith, voltage levels representing the previously stored binary digits. This operation is best understood by reference to the signal waveforms and patterns of Fig. 4. To carry out this function, dip-flop 39 has been triggered so that signal 44 is at high voltage level 44a and signal 40 is at low voltage level 40a. Gate circuits 46 and 47 are opened by high voltage level 44a of signal 44 while gate circuits 36 and 37 are closed, owing to low voltage level 40a of signal 4u'. The original charges on a series of spots are illustrated by the charge "9 levels of the pattern, generallydesignated 64 of Fig. .4, g while @the new chargelevels which are to` beplaced on the same series of spots are yillustrated by the pattern, generallydesignated 65 of Fig.` 4. The signal, generally desig- .natedl55f of Fig. 4 is the output signalofilip-op 41 after ,attenuation by network 55 and corresponds to thenew charge pattern-65, in the sense heretofore noted. Signal 55,'` wasderived from .the output signal (not illustrated) of flip-flop 53 in the same manner as that illustrated and 4`described in connection with the signals of Fig. 2 and re;)reducesY the binarydigits represented thereby.V

Duingvthe ifrstinterpulseinterval offsignal A214', low voltage level v55a of signal 55 is impressed'onlcoatingl() withthe result thatthe rst spot being scanned`,`of a negativev4 charge' level 64a, is discharged to positive charge level @Sqofpattern ,65. Thischange from negative to positive charge level produces a current flow in thel primary winding of transformer 28, which in `turn, produces apositive Nlevellq in the `output signal, generally designated 31 in f-lig. 4, of phase detector 31. Levelf31a was, Aas originally derivedfrom transformerr 28, modulated atl-l0` megacycles ,and v'afterdetection by detector 31, appears, as shown,.as l'adirect currentrlevel ofpositive Bvolts The reason for `thepoSIitiVe polarity has been set forth previously in connection with Lthe operation ofthe device in regenerating .the charge'levelsof the spots. The first voltagelevel 459a ofthe-signahgenerally designated 595m' Fig. v,4, appearing onoutput terminalk is one-'fourth'of Athe sum of level A3,1afof signall' and level`55dof signalf55, and thus, is of `a relatively highvoltage level l of ,approXimatelyE/ 4 volts. i Y' l During the second interpulse interval, high voltage Vlevel-55h of signal 55 `is, impressed on coating Ztl, and ,since the second spot scanned during this interval was originally at negative charge level 64b, the second ,spot 4does not -change in charge. VHence, substantially no outputsignal is produced by detector 31, as is indicatedfby zero voltage -level .31h of signal 31'. -Thus,fvoltage level 59ibof signal .159 duringfthis time interval is `derived solely fromhigh voltage level55b .of signaLSS, and is one-fourthofthe magnitudethereof andequal, in magnitude, to level597a. During the next interpulse interval, fthe third Vspot scanned :was `originally at positive `charge level-64e and is Achanged to negative charge level 165e oipatternY 65 by the high voltage -level 55p of Vsignal .55. This `changeof charge produces a negative voltage jlevelc of signal 31', Athe change .of jchargebeingof-.oppositerdirectionfto :that for the `firstspot ,contacted iduring `therst interpulse interval. The Vmagnitude of negative level 31C Iisgequal tothe magnitude of positive levella but of reversed polarity. The mixing vof high `voltage, level55c 4of signal-55' -and negative voltage level 31C ofV signal ,31' by resistors .56 l.and 57 produces a voltage levelic of signa1.59,level59c being, Vin effect, ya :cancellation of ,negativelevel 31e and high voltage` level 555C and .being,;.accordingly,:.of a..r.ela tively low voltage level ,comparedato `levelsz59tzand 59,b-;of

signal 59.

'The remaining voltagelevels of output signal U59 of WFig. `4'rr`1ay be readily `understoodfromihe explanation set forth vfor thefirst threeinterpulse' intervals. VThe fsignal, `generally designated 6G-of Pig. `4, illustrates the voltage levels `which wouldhave been produced 011.1the output lconductor :offdetector 3:1 from .charge '.patternz64 if no new charge pattermsuch as :thati represented: b.y pat tern 65, had been simultaneously placed onv layer 16. f Signa1166, Yalthough not actually'. appearing iinsthe device, serves. to illustrate thatoutput signal. 9.corresponds;to the voltage vlevels initially'on layer 416. Itis thus seen that output signalz59' represents the binaryIdigits originally storedonlayer 16.V

' Referring'nowto Fig. 5,there isherein'illustratedanother embodiment according yto *the present 'invention wherein the'memorytube comprises a-storage `tube 70. A4(,)onsiderable circuitry of the' storage device` of'FigJrS is :'tlenticaltotlie circuitry provided for the" device according according vto Fig. 1.

.to` Fig. `landfthe corresponding circuit elementsaregveri thev same numerals as previously but precede'drb'y fthe .digiti vvStorage tube includes a collector electrode72 anda target electrode 71 which has al thin layer vof Vdielectric material mounted on a metal backing so as ltoface .an electron beam 73. 'Electron beam 73 in 4this embodiment is unmodulated and is produced byahigh voltage source 521 connected to the electron gun of tube 70. A deflection system, identical to that shown in Fig. 1, cprnprisesV a pulse source 524 and stepped .waveform generator-S525 and 526 which are coupled to the horizontal and vertical deflection plates, respectively, of tube 70 andcaus'e beam `73 to strike the dielectric layer of targetelectrode 71 in a series of spots. i i i The output terminal ,of an attenuation network '555 is connected to collector electrode 72 while the 'metal backing of target electrode 71 is connected tc .ground through a resistor 74, the common junction of resistor 74 and electrode 71 being connected .to the input terminal of an amplifier 75. Amplier 75 isarranged, as for example, by Vhaving an odd number of stages. so as Vto invert the polarity of input signals between its input and output terminals. The output terminal `of amplier 75 is connected to the input ,terminal of a rst differentiating circuit 534 through a phase inverter `533 and to the input terminal of a second differentiating circuit 535. A mixing resistor 557y is connected lbetween the output terminal of amplifier 75 and output yterminal S59.

The principle of operation of storage tube '76 is slight- 1y different from that of cathode ray tube 11 of'Fig. 1. lf ilipfop 541 is producing its low voltage level, then la majority of the secondary emission electrons emitted from agiven spot under bombardment by electron beam 73 will return to the spot from which theywereliberated, there being no Vappreciable potential attraction on electrode 72. Thus, the given spot will, when beam 73 is removed, contain apsurplus of electrons and hence exhibit a relatively negative charge. Under -the same circumstances, if a high voltage level is produced by flip-op 541, then a majority of the secondary emission electrons will be drawn to collector electrode 72 with the result that the given spot under bombardment will, when the electron beam is removed, contain a deficiency of electrons and hence exhibit a relatively positive charge. Thus, the main dilference between the operation of cathode ray tube 11 `of Fig. 1 and storage tube 70 .of this embodimentV lies in the fact that, in theV former case, a high voltagelevelat flip-flop t1 produces a negatively charged spot, while in the latter case, a high voltage level at flip-flop 541 produces a positively charged spot.

The storage device, according to Fig. 5, may perform the identical functions as that described for the device Thus, a series of binary digits may be stored on target electrode 71 as a series of charged spots, respectively, and the manner of operation of.V the storage device of Fig. 5 to perform this operation is substantially identical to that described in connection with the lstorage device of Fig. l. For example, with flip-Hop 539 producing its high voltage vlevel o n output cmductor 544 `and thereby opening gate circuits 5436 and 5'47, the series of binary digits to be stored, as represented by theseries lof output voltage levels appearing on conductors 551 and 552 of flip-op 553, are reproduced by the output voltage levelsV of hip-dop S41.' With flip-op541 reproducing the series of output voltage levels vof ip-ilop 553, the series of spots contacted by beam thestorage device according to Fig. 5, is that of regenerating the charge on each of a series of spots, thespots having been previously :charged to represent a `series of binary digits. This function is performed when gate circuits 536 and 537 are opened by the production of a high voltage level signal on output conductor 540 of ip-flop 539. With this accomplished, if flip-flop 541 produces its low voltage level at the instant electron beam 73 contacts a spot having a positive charge, the given spot begins to absorb the emitted secondary emission electrons to assume the high voltage level of collector electrode 72 with the result that a corresponding electron ow from target electrode 71 to ground occurs through resistor 74. This current tiow results from the fact that the surface of the dielectric layer on target electrode 71 behaves as one plate of a condenser plate, the absorption of the electrons by the given spot under the above-stated conditions driving, through condenser action; a corresponding number of electrons from the metal backing to ground. This current flow results in a negative voltage drop across resistor 74 which is amplified and inverted into a positive signal by amplifier 75. The positive amplified signal is inverted into a negative signal by inverter 533 and, after differentiation by differentiating circuit S34, triggers flip-Hop 541 through its input conductor 542 into producing the appropriate high voltage level. The high voltage level, thus produced, returns the charge on the given spot back to its initial positive level.

If, on the other hand, iiip-flop S41 were producing its high voltage level at the instant a spot contacted by beam 73 had a negative charge, then a signal of positive polarity would be produced across resistor 74, owing, again, to the condenser action between the surface of the dielectric layer and the metal backing of target electrode 7i, since the spot would be, under the conditions stated, liberating electrons to collector electrode 72. This positive signal, in turn, after being inverted by amplifier 7S to a negative signal and the resulting negative signal after being diiierentiated by circuit 535, would trigger flip-flop Sell, through its input conductor 543, into producing its low voltage level thereby allowing the spot being contacted by the beam to return to its initial negative charge.

if the output voltage level produced by flip-flop 541 corresponds to the charge level on the particular spot being bombarded, then the conduction state of ii'ip-flop 541 is not changed and the spot assumes its exact initial charge as determined by the output voltage level of the flip-flop.

The final function capable of being performed by the device of Fig. is that of storing a new series of binary digits while simultaneously producing an output signal representing the series of previously stored binary digits. This function is accomplished when flip-op 539 is triggered to produce its high voltage level on output conductor 544 to thereby open gate circuits 546 and 547. The voltage levels appearing on output conductor 552 of iiip-fiop 553 and representing the new digits to be stored, are transferred, in the manner explained in connection with the device of Fig. l, to corresponding voltage levels appearing on the output conductor of flip-Flop 541.

If a given spot contacted by beam 73 has a charge level equal to the charge level corresponding to the new binary digit to be stored, then no output signal is produced across resistor '74 and the magnitude of the signal appearing on output terminal 559 is one-fourth of the value of the output signal of attenuation network S55 owing to the action of the mixing resistors 556 and 557 and output load resistor 569. if the spot contacted by beam 73 was previously charged positively and a negative charge is to be placed thereon, then a signal of negative potential would be produced across resistor 74. The negative signal is amplified and inverted by amplifier 75 into a corresponding positive signal, which, when mixed by the mixing network with the attenuated low voltage level of flip-flop 541, as applied to the collector electrode, produces a relatively high voltage level on output terminal 559 thereby indicating the originally stored digit. However, if the spot were originally charged negatively and a positive charge were to be stored thereon representing the new binary digit, then a positive signal would be produced across resistor 74, which after inversion by amplifier and mixing in the mixing network, results in an output signal on terminal 559 of a relatively low voltage level to thus indicate the digit originally stored.

As will be apparent to those skilled in the art, types of storage tubes other than those herein specifically illustrated, may be employed in the device according to the present invention. Also, types of mixing networks other than the resistor mixing network herein specifically illustrated may be employed without departing from the scope and spirit of the present invention, as defined in the appended claims.

What is claimed as new is:

l. In an electrostatic storage system including a memory tube having first and second electrodes, said first electrode having a spot thereon to be charged to one of two charge levels, the charge on said spot varying in accordance with the voltage level of the signal appearing on said second electrode, apparatus for selectively either regenerating the previous charge on said spot 0r storing a new charge on said spot, said apparatus cornprising: actuable means responsive to successive input signalsV for producing an electrical signal having alternate high and low voltage levels corresponding to the two charge levels, respectively; means for applying said electrical signal to the second electrode; output means electrically coupled to one of the electrodes for producing an output signal when the charge level on the spot does not correspond to the voltage level of said electrical signal; first selectively operable means for applying said output signal to said actuable means to actuate said actuable means to produce the voltage level corresponding to the previous charge level on the spot; second selectively operable means coupled to said actuable means for actuating said actuable means to produce the voltage level corresponding to the new charge level for the spot; and means coupled to said first and second selectively operable means for selectively operating said first and second selectively operable means, whereby the previous charge level on the spot will either be regenerated or changed to the new charge level, respectively.

2. The system according to claim l wherein said memory tube comprises a cathode ray tube, said first electrode comprises a secondary emissive layer within said tube, and said second electrode comprises an external conductive coating adjacent the layer, said one electrode being said second electrode.

3. The system according to claim 1 wherein said memory tube comprises a storage tube, said first electrode comprises a target electrode, and said second electrode comprises a collector electrode, said one electrode being the target electrode.

4. The apparatus defined in claim l, having, in addition, an output terminal; first means for applying said output signal to said output terminal; and second means for applying said electrical signal to said output terminal whereby the signal appearing on said output terminal represents the original charge on the spot during the operation of either of said first and second selectively operable means.

5. A circuit for use with a memory tube having first and second electrodes, said circuit selectively either regenerating the previous charge on a spot on the first electrode and producing an output signal representing the previous charge, or storing a new charge on the spot while simultaneously producing an output signal representing the previous charge, said spot having been previously charged to one of two charge levels, the charge on said spot being variable in accordance with the voltage level of the electrical signal appearing on the second electrode, said new 'charge beingeither ofsaid two charge v-levfels, said;` circuit comprising: actuablemeans having 'first andsecond input lterrninals,andanl output conductor, said actuable means being responsive to` signals applied to said first vand' secv-ond input terminalswfor .producing` a first output signal having high .and low voltage levels, respectively, on `said `.output conductorysaid high and low voltage `levels corl-.responding to the tworcharge levels, iresp'ectively;;means electrically coupling said output conductor to the second electrode; `output means electrically coupled to one of the ,ielectrodesfor producing a second :output signal represent- :ingrthefchange .o'f charge lonzthespot; means` for inverting ,fsaidsecondcutput signal; first vselectively operablemeans .for applying said secondoutput signal andthe inverted ,secondoutput signal to said rst and second input terminals, 'respectively,of, said ,actuable means to actuate .saidractuablemeans to set said `first output signal to a voltage levelcorresponding to the Iprevious charge on the spot; lsecond nselectivelyoperable means `coupled to said first and second input terminals `for actuating said actuable 1meansto set 'said first outputzsignal to a voltage level -correspondingtothe newfcharge, for the spot; means for .selectively rendering operable said rst and said second selectively, operable means whereby the previous charge Aon the spot Awill either'be regenerated ,or charged to the `new `charge,jrespectively; and` means for combining said vtirstand secondoutputvsignals to produce an electrical signal-representing thelprevious ,charge on the spot during the actuationeither .of said first or second selectively operable means.

comprises afcollector electrode, said one electrode being t ,the target relectrode.

8.- A circuit `for use with a memory tube having Vfirst `,and zsecondrelectrodes, `said circuit selectively eitherre- 'generatingzthe previous charge on a spot ontheafirstelec` =trode v.andx producing ,anoutput signal representing the previous charge, Vor storing, a new `charge on the spot while simultaneously producing an output signalrepresentingthe previous zcharge, saidspot charging and vrhaving beenpreviously charged to one oftwo charge levelsthe :charge on the'spot being variable in accordance with the voltage-level of theV electrical signal appearing on -the -secondielectrode, said circuit comprising: a bistable fiiplflop havingf'firstand second input terminalsrandan out- ;.put conductor, .said flip-Hop being responsive to signals applied to said first and second input terminals for producing a first electrical output signal having first and second yvoltage levels,` respectively, on said Voutput conductor;

an attenuation network coupled between saidv output conductorLand the second electrode for attenuating the first and second voltage levelsof said first output signal to cor- .lrespoxnd to; the 'two ,charge levels, respectively; output .rmeans electrically .coupled to one of theelectrodes, for

,producing a second electrical output signal representing the change-ofcharge on the spot; first means coupled to `ysaid outputmeans for differentiating said second elecutrical output signal; second means coupled to said output means for inverting said second electrical output signal; :third means coupled to said second means for differentiating the vkinverted second electrical output signal; first 1 ,selectively,;operable means coupled to said first and sece ond meansfor applying the differentiated second electrical output signalrand-,the differentiated inverted second electlrical output signal to said first and secondinput terminals, .\1'espectiv^ely, to set said first Velectrical.outputrsignal to a voltage level corresponding to the previous chargelevel 14 on the spo'tg'second selectively operable means coupled to said first and second input fterminalsgfor setting said first electrical output signal-to a voltage level correspondingto the -new charge for the spot; means coupled to said first and second selectivelymoperable means for selectively rendering operable saidfirst and said second selectively operable means, whereby the previouscharge ,on the spot will either be regenerated or changed tothe *new charge, respectively; an outputterminal; first resistor means electrically coupled `between the secondfelectrode and said output terminal; second resistor means;and `means-for electrically coupling said second resistor means between Asaid one electrode, and said output terminal, whereby the signalV appearing-on said .output terminal represents the previous charge on the spot during the actuation of either of said rst and second selectively operable means.

9. A circuit for use with ajmemory tube having first andsecond electrodes, said-circuitcharging a spot on the first electrode to either of twocharge levels corresponding to two voltageV levels, respectively,lof an input signal, the charge on said spot "being previously at one of the two charge levels and varying in accordance with the voltage level of theelectricalsignal appearing on the second-electrode, said circuit producing .an output signal representing the previous `charge and comprising: input means ,of

, applying the inputsignal `tothe second electrode; output means electrically coupled to one of the electrodes for `producing an output signal representing the change 0f charge on the spot in response to the applied input signal;

and means coupled to-said input means and to said out- ,levels, said circuit producing an output signal representing the previous charge and comprising: a dip-flop havingan output conductor, said flip-flop producing an output signal having either a first-or a second output voltage level on said output conductor; an attenuation network conductively coupled between said output conductor and the second electrode for attenuating the first and second output voltage `levels of said Hip-flop vto correspond to the two charge levels, respectively; input means coupled to said flip-flop for triggering said flip-flop so that the output voltage level of said-output signal corresponds to the new charge to bestored on the spot; output means electrically coupled to one of the electrodes for producing an output signalrepresenting the change of charge on the spot; an output terminal; first and second resistors; means electrically coupling one end of each of said first and second resistors to said output terminalg-,meanselectrically coupling the other end of said first resistorl to the second electrode; and means electrically coupling said one electrode to the other end of said second resistor p whereby the voltage level of the signalappearing on said output terminal represents the original `charge on the `spot.

e il. Acircuitfor use with a cathode ray tube having aV Vsecondary emissive layer and an external conductive coating adjacent the layer, said circuit being adapted to store a new charge on a spot on the layer, the charge on said spot varying in accordance with the voltage appearing on the conductive coating, said spot having been previously charged, jsaid circuit comprising: input means for applyingta first electrical signal -having a voltage level correspondingto the new charge to the conductiveV coating; outputmeans electrically coupled to the conductive l coating forproducing a second electrical signal representing the change of charge on the spot in response to said first electrical signal; and means coupled to said input means and to said output means for combining said first and second electrical signals to produce an electrical output signal representing the original charge on the spot.

12. A circuit for use with a cathode ray tube having a phosphorescent layer, an external conductive coating adjacent the layer, and means for producing an electron beam current modulated by a radio-frequency signal, said circuit storing a new charge on a spot on the layer, the charge on the spot varying in accordance with the voltage level of the electrical signal appearing on the conductive coating, said spot having been previously charged to one of two charge levels, said circuit producing an output signal representing the previous charge and comprising: means for applying a rst electrical signal having a voltage level corresponding to the new charge for the spot to the conductive coating; output means electrically coupled to the conductive coating for producing a second electrical signal representing the change of charge on the spot as modulated at the frequency of the radio-frequency signal; detector means electrically coupled to said output means for producing a third'electrical signal corresponding to the envelope of the modulated signal; an output terminal; first resistor means for applying said third electrical signal to said output terminal; and second resistor means for applying said first electrical signal to said output terminal whereby the voltage level of the signal appearing on said output terminal represents the previous charge on the spot.

13. A circuit for use with a cathode ray tube having a phosphorescent layer, an external conductive coating adjacent the layer, and means for producing an electron beam current modulated by a radio-frequency signal, said circuit storing a new charge of one of two charge levels on a spot on the layer, the charge of said spot varying in accordance with the voltage level of the signal appearing on the conductive coating, said spot having been previously charged to one of said two charge levels, said circuit producing an output signal representing the previous charge and comprising: a flip-flop having an output conductor and producing an output signal having either a first or a second output voltage level on said output conductor; an attenuation network electrically coupled between said output conductor and the conductive coating for attenuating the first and second output voltage levels of said iiip-flop output signal to correspond to the two charge levels, respectively; a transformer having a primary and a secondary winding; means for coupling said primary winding to the conductive coating, the signal appearing across said Secondary winding representing the change of charge on the spot modulated at the frequency of the radio-frequency signal; a phase detector having a pair of input circuits and an output circuit, said phase detector being responsive to unmodulated and modulated signals of identical carrier frequencies applied to said input circuits for producing a signal representing the envelope of the modulated signal across said output circuit; a radio-frequency amplifier electrically coupled between said secondary winding and one input circuit of said phase detector; means for applying the radio-frequency signal to the other input circuit of said phase detector whereby the signal appearing across the output circuit of said phase detector represents the change of charge on the spot; an output terminal; first resistor means electrically coupled between the conductive coating and said output terminal; and second resistor means electrically coupled between the output circuit of said phase detector and said output terminal whereby the signal appearing on said output terminal represents the previous charge on the spot.

14. A circuit for use with a storage tube having target and collector electrodes, :said circuit charging a spot on the target electrode to one of two charge levels corresponding to the voltage level of an input signal, applied to the collector electrode, said spot having been previously charged to one of said two charge levels, said circuit comprising: input means for applying the input signal to the collector electrode; output means electrically coupled to said target electrode for producing an output signal representing the change of charge level on the spot in response to the applied input signal; and means coupled to said input means and to said output means for combining the output signal and the input signal to produce an electrical signal representing the original charge level on the spot.

l5. A circuit for use with a storage tube having a co1- lector and a target electrode, said circuit storing a new charge on a spot on the target electrode, the charge on said spot varying in accordance with the voltage level of the signal appearing on the collector electrode, said spot having been previously charged to one of said two charge levels, said :circuit producing an output signal representing the previous charge level on the spot and comprising: a flip-flop having an output conductor, said flip-flop producing a first electrical signal having either a first or a second output voltage level on said output conductor; an attenuation network electrically coupled between said output conductor and the collector electrode for attenuating the first and second output voltage levels of said first electrical signal to correspond to the two charge levels, respectively; means for triggering said flip-flop so that the output voltage level of said first electrical signal corresponds to the new charge level to be stored on the spot; resistor means electrically coupled to said target electrode, the signal appearing across said resistor means representing the change of charge level on the spot; an output terminal; first yand second resistors; means electrically coupling one end of each of said first and second resistors to said output terminal; means electrically coupling the other end of said first resistor to the collector electrode; and means electrically coupling the target electrode to the other end of said second resistor whereby the signal appearing on said output terminal represents the previous charge level on the spot.

16. A circuit for use with a memory tube having first and second electrodes, said circuit regenerating the charge on a spot on the first electrode, the charge on said spot varying in accordance with the voltage level of the signal appearing on the second electrode, said spot having been previously charged to one of two charge levels, said circuit comprising: actuable means responsive to successive input signals for producing a first electrical signal having alternate first and second voltage levels corresponding to the two charge levels, respectively; means for applying said rst electrical signal to the second electrode; output means electrically coupled to one of the electrodes for producing an output signal when the previous charge on the spot does not correspond to the voltage level of said first electrical signal; and means for applying the output signal to said actuable means to actuate said actuable means to produce the voltage level corresponding to the previous charge level on the spot.

17. A circuit for use with a memory tube having first and second electrodes, said circuit regenerating the charge on a spot on the first electrode, the charge on said spot varying in laccordance with the voltage level of the signal appearing on the second electrode, said spot having been i previously charged to one of two charge levels, said circuit comprising: actuable means having first and second input conductors and an output conductor and responsive to signals applied to said first and second input conductor for producing a first electrical output signal having first and second voltage levels, respectively, said first and second voltage levels corresponding to the two charge levels, respectively; means electrically coupling said output conductor to the second electrode; output means electrically coupled to one of the electrodes for producing a second electrical output signal representing the change of charge on the spot; first means for applying said second electrical QUput signal to said first input conductor; means for in- 17 verting said second electrical output signal; means for applying the inverted second electrical output signal to said second input conductor whereby said actuable means is actuated to produce a third electrical output voltage level corresponding to the previous charge level on the spot.

18. A circuit for use with a memory tube having first and second electrodes, said circuit regenerating the charge on a spot on the first electrode, the charge on said spot varying in accordance with the voltage level of the signal appearing on the second electrode, said spot having been previously charged to one of two charge levels, said circuit comprising: a bistable flip-flop having first and second input conductors and an output conductor, said ip-op being responsive to signals applied to said first and second input conductors for producing on said output conductor a first electrical output signal having first and second voltage levels, respectively; an attenuation network coupled between said output conductor and the second electrode for attenuating the first and second voltage levels of said first output signal to correspond to the two charge levels, respectively; output means electrically coupled to one of the electrodes for producing a second electrical output signal representing the change of charge on the spot; first means for differentiating said second electrical output signal; means for inverting said second electrical output signal; second means for differentiating the inverted second electrical output signal; and means for applying the differentiated second electrical output signal and the differentiated inverted second electrical output signal to said first and second input conductors, respectively, to produce on said output conductor an output signal having a voltage level corresponding to the previous charge on the spot.

19. A circuit for regenerating the charge on a spot on the secondary emissive layer of a cathode ray tube, said tube having, in addition, an external conductive coating adjacent the layer, the charge on said spot varying 1n accordance with the voltage level of the signal appearlng on the conductive coating, said spot having been previously charged to one of two charge levels, said circuit comprising: actuable means responsive to successive .input signals for producing a irst electrical signal having alternate rst and second 'voltage levels, said rst and second voltage levels corresponding to the two charge levels, respectively; means for applying said rst electrical signal to the conductive coating; output means electrically coupled to the conductive coating for producing a second electrical signal when the voltage level of said first electrical signal does not correspond to the previous charge level on .the spot; and means for applying said second electrical signal to said actuable means to actuate said actuable means into producing an output voltage level corresponding to the previous charge on the spot.

20. A circuit for use with a cathode ray tube having a phosphorescent layer, means for producing an electron beam current modulated by a radio-frequency signal, and an external conductive coating adjacent the layer, said circuit regenerating the charge on a spot on the layer, the charge on said spot varying in accordance with the voltage level of the signal appearing on the conductive coating, said spot having been previously charged to either of two charge levels, said circuit comprising: actuable means having first and second input conductors and an output conductor and being responsive to signals applied to said first and second input conductors for producing a first electrical signal having first and second voltage levels, respectively, on said output conductor, said first and second voltage levels corresponding to the two charge levels, respectively; a transformer having primary and secondary windings; means coupling said output conductor and said primary winding to the conductive coating, the signal appearing across the secondary winding of said transformer representing the change of charge n the spot modulated at the frequency of the radiofrequency signal; detector means coupled to said secondary winding for producing a second electrical signal representing the envelope of the modulated signal; means for inverting said second electrical signal; and means for applying said second electrical signal and the inverted second electrical signal to said first and second input conductors, respectively, to produce on said output conductor a signal having a voltage level corresponding to the previous charge on the spot.

2l. A circuit for use with a cathode ray tube having a layer, an external conductive coating adjacent the phosphorescent layer, land an electron beam current modulated by a radio-frequency signal, said circuit regenerating the charge on a spot on the layer, the charge on said spot varying in accordance with the voltage level of the signal appearing on the conductive coating, said spot having been previously charged to one of two charge levels, said circuit comprising: a bistable flip-flop having first and second input conductors and an output conductor; an attenuation network coupled between said output conductor and the conductive coating; a transformer having primary and secondary windings; means electrically coupling said primary winding to said conductive coating, the signal appearing across said secondary winding representing the change of charge on the spot modulated at the frequency of the radio-frequency signal; a phase detector having a pair of input circuits and an output circuit, said phase detector being responsive to unmodulated and modulated signals of identical carrier frequencies applied to the input circuits thereof for producing an electrical output signal representing the envelope of the modulated signal on the output circuit thereof; means for coupling said secondary winding to one input circuit of said phase detector; means for applying the radio-frequency signal to the other input circuit of said phase detector whereby the signal von the output circuit of said phase detector represents the change of charge on the spot; first differentiating means electrically coupled between the output circuit of said phase detector and the first input conductor of said flip-flop; and second differentiating means electrically coupled between the output circuit of saidvphase detector and the second input conductor of said flip-flop, said second differentiating means including a serially-connected phase inverter, said flip-flop being operable in response to signals applied to said first and second input conductor to produce an output signal having a voltage level corresponding to the previous charge on the spot.

22. A circuit for regenerating the charge on a spot on the target electrode of a storage tube, said storage tube having, in addition, a collector electrode, the charge on said spot varying in accordance with the voltage level of the signal appearing on the collector electrode, said spot having been previously charged to one of two charge levels, said circuit comprising: actuable means electrically coupled to the collector electrode and responsive to successive input signals for producing an electrical signal having alternate first and second voltage levels corresponding to the two charge levels, respectively; output means electrically coupled to the target electrode for producing a first output signal representing the change of charge on the spot; and means for applying said first output signal to said actuable means to actuate said actuable means to make the voltage level of said electrical signal correspond to the previous charge on the spot.

23. A circuit fior regenerating the charge on a spot on Ithe target uelectrode of a storage tube, said storage tube having, lin addition, a collector electrode, the charge on said spot varying in accordance with t-he voltage appearing on the collector electrode, said spot having been pneviously charged to tone of rtvwo charge levels, said circuit comprising: 'actwa'ble means having first :and second input conductors 'and an output conductor and responsive to signals applied to said first and .second input conductors for producing yan electrical signal having first and second voltiage leveis, ire'spectively, on lsaid ioutput conductor, said first `and `second voltage levels corresponding to the two `charge levels, respectively; means electrically coupling ysaid loutput conductor io the collector electrode; ioutput means `electrically coupled to the target electrode for producing Vain output `signal representing the change `of charge ron the spot; rst rneanfs for applying `the output signal to :said ist input conductor; yand second means for inverting lthe output signal and applying the inverted `output .signal to said second input conductor whereby the electrical signal from said act-liable means has Ia voltage level corresponding to the previous charge on the spot.

24. A circuit for regenerating the charge ion a spot fon the target electrode :of a storage tube, said :storage tube having, in addition, `a collector electrode, 'the charge on the spot varying in yaccordance with the voltage `appearing en the collector electrode, said spot having been previlously charged to `one of two charge levels, said circuit comprising: `a bistable ilip-fop having irst and second References Cited in the file of this patent UNITED STATES PATENTS 2,527,652 Pierce Oct. 31, 1950 2,572,586 Barney Oct. 23, 1951 2,589,460 Tuller Mar. 1,8, 1952 2,639,425 Russell 4et lal. May 19, 1953 

